The present invention relates to a numerically controlled lathe which has two opposed head stocks, main shafts respectively supported by the two head stocks, and two tool rests each having attached thereto a tool used to machine a workpiece grasped by each of the main shafts, and can simultaneously machine two workpieces grasped by the respective main shafts on the two head stocks, and to a method of cutting a workpiece on this numerically controlled latch.
A numerically controlled lathe (which will be referred to as an NC lathe hereinafter) which has two opposed head stocks and tool rests and can simultaneously machine two workpieces grasped by main shafts of the two head stocks by using a tool attached to each of the tool rests is known from, for example, Japanese Patent Application Laid-open No. 501758/1998 and others.
FIG. 13 is a plane view illustrating a schematic structure of the NC lathe disclosed in Japanese Patent Application Laid-open No. 501758/1998.
A first head stock 220 and a second head stock 230 are oppositely arranged on a bed 210 of an NC lathe 200. The first head stock 220 and the second head stock 230 respectively rotatably support main shafts 221 and 231 parallel to a Z axis of the NC lathe 200. These main shafts 221 and 231 are arranged so as to be eccentric in the direction of an X axis. A non-illustrated chuck is provided at an end of each of the main shafts 221 and 231, and the chucks grasp workpieces W1 and W2.
The first head stock 220 is fixed to the bed 210. A guide rail 240 extending in the direction of a Z1 axial line parallel to the Z axis of the NC lathe 200 is provided to the bed 210. A saddle 250 is mounted on the guide rail 240, and the saddle 250 moves forward and backward in the direction of the Z1 axis while being guided by the guide rail 240 by drive of a non-illustrated drive mechanism including a servo motor and others.
A guide rail 270 is provided on the saddle 250 in the direction parallel to the X axis. A carriage 255 which reciprocates along the guide rail 270 is mounted on the guide rail 270. This carriage 255 moves in the direction of an X1 axis parallel to the X axis by drive of the non-illustrated drive mechanism including a servo motor and others. A first tool rest 260 and the second head stock 230 are mounted on the carriage 255 and move together with the carriage 255 in the direction of the X1 axis.
The first tool rest 260 includes a turret face plate 261 capable of sectional rotation on one side thereof. To this turret face plate 261 are attached a plurality of tools T1 used to machine the workpiece W1 grasped by the main shaft 221 of the first head stock 220. Further, the tool T1 is positioned with respect to the workpiece W1 and machines the workpiece W1 while moving the direction of the Z1 axis by a combination of movement of the saddle 250 in the direction of the Z1 axis and movement of the first tool rest 260 in the direction of the X1 axis.
A second tool rest 280 is provided so as to be opposed to the main shaft 231 of the second head rest 230. A turret face plate 280 capable of sectional rotation is provided to the second tool rest 280 on one side thereof. To the turret face plate 281 are attached a plurality of tools T2 used to machine the workpiece W2 grasped by the main shaft 231 of the second head stock 230. The second tool rest 280 can freely move on the bed 210 in the direction of the X2 axis along a guide rail 282 provided in the direction of an X2 axis parallel to the X axis of the NC lathe 200.
According to such an NC lathe 200, since the first tool rest 260 and the second head stock 230 are provided on the common saddle 250 and the carriage 255, movement of the tool T1 in the direction of the Z1 axis relative to the workpiece W1 becomes movement of the tool T2 relative to the workpiece W2, and the same drilling or the like can be carried out with respect to the two workpieces W1 and W2 at the same time.
Furthermore, different kinds of machining can be performed to the workpieces W1 and W2 at the same time by adding a movement speed inherent to the direction of X2 axis to the tool T2 while moving the tool T2 such as a cutting tool in the direction of the X2 axis in synchronization of movement of the tool T1 in the direction of the X1 axis.
The above-described NC lathe 200 can perform the same kind or different kinds of machining to a plurality of workpieces W1 and W2 at the same time, but there are the following disadvantages.
That is, since movement speeds of the tool T1 and the tool T2 in the direction of the Z1 axis are determined by movement of the saddle 250 in the direction of the Z1 axis, types of machining to the workpieces W1 and W2 which can be performed at the same time are restricted.
It is an object of the present invention to provide an NC lathe which can perform various kinds of machining to a workpiece on the first main shaft side and a workpiece on the second main shaft side at the same time, and a method of cutting a workpiece on this NC lathe.
According to the present invention, there is provided a numerically controlled lathe having: a first head stock and a second head stock arranged so as to be opposed to each other; a first main shaft supported by the first head stock and a second main shaft supported by the second head stock; a tool rest including tools used to machine workpieces grasped by the first main shaft and the second main shaft; and a numerical control device which controls rotation of the first main shaft, rotation of the second main shaft and relative movement of the tool rest with respect to the first head stock or the second head stock, wherein the numerically controlled lathe comprises: a first tool rest to which one or both of a first tool used to machine the workpiece grasped by the first main shaft and a second tool used to machine the workpiece grasped by the second main shaft can be attached and can freely move in a direction of a Z1 axis parallel to a main shaft axial line of the first main shaft and a direction of an X1 axis orthogonal to the Z1 axis; a second head stock which can freely move in a direction of an X3 axis parallel to the X1 axis of the first tool rest and a direction of a Z3 axis parallel to the Z1 axis; and a second tool rest to which one or both of a third tool used to machine the workpiece grasped by the first main shaft and a fourth tool used to machine the workpiece grasped by the second main shaft can be attached and can freely move in a direction of a Z2 axis parallel to the main shaft axial line of the first main shaft and a direction of an X2 axis orthogonal to the Z2 axis.
In this numerically controlled lathe, there is provided a control device which includes a first control system which controls movement of the first tool rest in the direction of the X1 axis and movement of the same in the direction of the Z1 axis, a second control system which controls movement of the second head stock in the direction of the X3 axis and movement of the same in the direction of the Z3 axis and a third control system which controls movement of the second tool rest in the direction of the X2 axis and movement of the same in the direction of the Z2 axis, and it is good enough that the first control system, the second control system and the third control system perform superposition control of movement of a pair of the X1 axis and the X3 axis, superposition control of movement of a pair of the X3 axis and the X2 axis, superposition control of movement of a pair of the Z1 axis and the Z3 axis, and superposition control of movement of a pair of the Z3 axis and the Z2 axis in accordance with combinations of three tools from the tools T1 to T4 used to machine the workpiece W1 and the workpiece W2.
According to the present invention, there is provided a cutting method of using the numerically controlled lathe having the above structure, comprising the steps of: enabling one or both of a first tool used to machine a workpiece grasped by the first main shaft and a second tool used to machine a workpiece grasped by the second main shaft to be attached to the first tool rest; enabling one or both of a third tool used to machine the workpiece grasped by the first main shaft and a fourth tool used to machine the workpiece grasped by the second main shaft to be attached to the second tool rest; superposing movement of the second headstock in the direction of the X3 axis or the direction of the Z3 axis on movement of the first tool rest in the direction of the X1 axis and movement of the same in the direction of the Z1 axis; superposing movement of the second tool rest in the direction of the X2 axis or the direction of the Z2 axis on movement of the second head stock in the direction of the X3 axis or movement of the same in the direction of the Z3 axis; and simultaneously machining the workpieces grasped by the first main shaft and the second main shaft by using the tools attached to the first tool rest and the second tool rest, when the first tool and the second tool are attached to the first tool rest and the fourth tool is attached to the second tool rest.
According to the present invention, the workpiece on the first head stock is machined by using the first tool while the first tool rest is moving in the direction of the X1 axis and the direction of the Z1 axis. Since the second head stock can move in the same direction as the first tool rest, relative movement of the second tool attached to the first tool rest and the workpiece on the second head stock can be set to 0 by synchronizing the second head stock to movement of the first tool rest.
Moreover, in order to obtain movement required for machining the workpiece W2 using the second tool, movement of the second head stock in the direction of the X3 axis is superposed on movement of the first tool rest in the direction of the X1 axis, and movement of the second head stock in the direction of the Z3 axis is superposed on movement of the first tool rest in the direction of the Z1 axis. As a result, final movement of the second head stock can be determined.
Likewise, since the second tool rest can move in the same direction as the second head stock, relative movement of the fourth tool attached to the second tool rest and the workpiece on the second head stock can be set to 0 by synchronizing the second tool rest with movement of the second head stock.
In addition, in order to obtain movement required for machining the workpiece using the fourth tool, movement of the second tool rest in the direction of the X2 axis is superposed on movement of the second head stock in the direction of the X3 axis, and movement of the second tool rest in the direction of the Z2 axis is superposed on movement of the second head stock in the direction of the Z3 axis, thereby determining final movement of the second tool rest.
In this manner, the workpiece of the first main shaft and the workpiece of the second main shaft can be simultaneously machined by using the tool attached to the first tool rest and the tool attached to the second tool rest. The machining of the workpiece on the first main shaft side may be the same as that of the workpiece on the second main shaft side, but they may be different from each other.